parse-server has GraphQL complexity validator exponential fragment traversal DoS

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.2 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-34573: 0.64% estimated exploitation activity in the next 30 days; percentile 50.85 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact The GraphQL query complexity validator can be exploited to cause a denial-of-service by sending a crafted query with binary fan-out fragment spreads. A single unauthenticated request can block the Node.js event loop for seconds, denying service to all concurrent users. This only affects deployments that have enabled the requestComplexity.graphQLDepth or requestComplexity.graphQLFields configuration options. Patches The fix replaces the per-branch fragment traversal with memoized fragment computation, reducing the traversal from exponential O(2^N) to linear O(N) time. Additionally, early termination aborts the traversal as soon as configured limits are exceeded. Workarounds Disable GraphQL complexity limits by setting requestComplexity.graphQLDepth and requestComplexity.graphQLFields to -1 (the default). Resources - GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-mfj6-6p54-m98c - Fix Parse Server 9:…

Published by the source

31 Mar 2026, 23:49 UTC

Last modified by the source

6 Apr 2026, 15:27 UTC

Source last checked

26 Oct 2026, 12:47 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-mfj6-6p54-m98c

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-mfj6-6p54-m98c

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# Patch Next advisory brief: CVE-2026-34573

Advisory: parse-server has GraphQL complexity validator exponential fragment traversal DoS
IDs: CVE-2026-34573, GHSA-mfj6-6p54-m98c
Record: https://patchnext.com/advisories/cve-2026-34573 (revision 3, source checked 26 Oct 2026, 12:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: parse-server 9.7.0-alpha.12, 8.6.68. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm parse-server: affected >= 9.0.0, < 9.7.0-alpha.12; < 8.6.68; fixed in 9.7.0-alpha.12, 8.6.68

## Suggested inspection (read-only)
- `npm ls parse-server --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on parse-server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-mfj6-6p54-m98c (OSV record GHSA-mfj6-6p54-m98c lists affected ranges: npm parse-server >=9.0.0 =0 <8.6.68 (fixed))
- Verified: https://github.com/advisories/GHSA-mfj6-6p54-m98c (GitHub-reviewed advisory GHSA-mfj6-6p54-m98c lists affected ranges: npm parse-server >=9.0.0 =0 <8.6.68)

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